1. Field of the Invention
The present invention relates to a semiconductor device testing apparatus and method, and in particular to a semiconductor device testing apparatus equipped with a power supply unit capable of outputting a low-noise DC voltage.
2. Description of the Related Art
FIG. 1 is a block diagram showing a conventional power supply unit 30. The power supply unit 30 includes an AC-DC power supply 40 and a capacitor C1. The AC-DC power supply 40 receives AC voltage from an AC power supply 220, and then converts it to DC voltages VDD and VSS (VDD greater than VSS) so as to supply the DC voltage to a semiconductor device 200 placed on a device contact portion 90 of a semiconductor device testing apparatus. The capacitor C1 is provided between the AC-DC power supply 40 and the semiconductor device 200, connects the VDD and VSS and charges or discharges the DC voltage supplied from the AC-DC power supply 40.
The capacitor C1 is small sized and of large capacity. By inserting the C1 between the VDD and VSS, the noise contained in the DC voltage supplied from the AC-DC power supply can be reduced.
In the conventional practice, a switching power supply, dropper power supply and so on are used as the AC-DC power supply 40. Advantageous aspects of the switching power supply lies in being small sized and having a desirable conversion efficiency while the advantageous aspect of the dropper power supply is that a voltage noise is small.
There are occasions where the low-noise voltage needs to be supplied to the semiconductor device 200 for certain types of semiconductors under test and certain testing procedures. For instance, when testing an analog circuit as the semiconductor device 200, especially, a high-speed analog circuit such as a video circuit and so on, the noise contained in the supplied voltage affects the test in a negative manner and eventually leads to inaccurate test results. Therefore, there are many occasions where the dropper power supply which outputs the low-noise voltage is used when testing the analog circuits or the like requiring the low-noise voltage supply.
However, since the unwanted power is radiated in the form of the heat in the dropper power supply, the conversion efficiency is very low. Besides, a radiator need be further provided. On the other hand, though the switching power supply is small sized and has a desirable conversion efficiency, a switching noise is caused because an oscillator provided in the power supply constantly oscillates. Hence, usage of the switching power supply is not desirable when a test requires the supply of low-noise voltage. Thus, it has been hoped to provide a small sized switching power supply having desirable conversion efficiency and capable of supplying the low-noise voltage.
Therefore, it is an object of the present invention to provide power supply unit, semiconductor device testing apparatus and semiconductor device testing method which overcome the above issues in the related art. This object is achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to one aspect of the present invention, there is provided a power supply unit which supplies voltage to electric components, comprising: a DC power supply which supplies DC voltage to the electric components; a capacitor, provided between said DC power supply and the electric components, which charges the DC voltage; an input switch which connects or disconnects the capacitor and the DC power supply; and a switching control unit which charges the capacitor by switching the input switch ON, and supplies power charged in the capacitor to the electric components by switching the input switch OFF.
According to another aspect of the present invention, there is provided semiconductor device testing apparatus for testing a semiconductor device, comprising: a device contact portion which places the semiconductor device and inputs an input signal pattern to the semiconductor device; a DC power supply which supplies DC voltage to the semiconductor placed on the device contact portion; a capacitor which charges or discharges the DC voltage between the power supply and the semiconductor device; an input switch which connects or disconnects the capacitor and the DC power supply; a switching control unit which makes the capacitor charged with the DC voltage by switching the input switch ON, wherein switching control unit supplies the DC voltage charged in the capacitor by switching the input switch OFF, and wherein the switching control unit further includes a pattern generator which supplies the input signal pattern to the semiconductor device in the event that the switching control unit switches the input switch OFF and an output switch ON, where the output switch connects or disconnects the capacitor and the semiconductor device.
Moreover, the semiconductor device testing apparatus may further comprise an output switch which connects or disconnects the capacitor and the semiconductor device, wherein the switching control unit makes the capacitor charged with the DC voltage by switching the output switch OFF and switching the input switch ON, and wherein the switching control unit supplies the DC voltage charged in the capacitor to the semiconductor device by switching said output switch ON and switching the input switch OFF.
Moreover, the pattern generator may further comprise: an input signal pattern supplying unit which supplies the input signal pattern to the semiconductor device in the event that the switching control unit switches the output switch an the input switch ON, and wherein the switching control unit makes the input switch temporarily OFF in the event that the input signal pattern is being supplied to the semiconductor device.
Moreover, the semiconductor device testing apparatus may further comprise: a plurality of the capacitors, provided in parallel between said DC power supply and the semiconductor device, which charge the DC voltage; and a plurality of the output switches which connect or disconnect a plurality of the capacitors and the semiconductor device, and wherein the switching control unit, with one of said plural output switches being ON, makes other output switches OFF, while one of the plural output switches is being ON and the DC voltage charged in said capacitor is being supplied to the semiconductor device via the output switch having been ON.
Moreover, the semiconductor device testing apparatus may further comprise a plurality of the input switches which connect or disconnect the plural capacitors and the DC voltage respectively, wherein the switching control unit, with one of the plural input switches being ON, makes other input switches OFF while one of the plural input switches is ON and the DC voltage is charged from the DC power supply to the capacitor via the input switch having been ON.
It is preferable that the input switch, output switch and capacitor be provided removably so as to be replaced anew.
Preferably, the DC power supply is an AC-DC power supply which converts AC voltage supplied from an AC power supply, to DC voltage.
According to still another aspect of the present invention, there is provided a semiconductor device testing method of testing a semiconductor device using semiconductor device testing apparatus, the method comprising: charging DC voltage to a capacitor; and testing the semiconductor device by: disconnecting supply of the DC voltage to the capacitor; and inputting an input signal pattern to the semiconductor device while the DC voltage charged in the capacitor is being supplied to the semiconductor device.
Preferably, the charging includes charging the DC voltage to a first capacitor and a second capacitor, and the testing includes: disconnecting supply of the DC voltage to the first capacitor; and inputting the input signal pattern to the semiconductor device while the DC voltage charged in the first capacitor is being supplied to the semiconductor device. Moreover, the semiconductor device testing method may further comprise: stopping input of the input signal pattern to the semiconductor device; disconnecting supply of the DC voltage charged in the first capacitor to the semiconductor; replacing the semiconductor device with other semiconductor device; connecting the second capacitor to the replaced semiconductor device in order to supply the DC voltage charged in the second capacitor to the replaced semiconductor device.
Moreover, the semiconductor device testing method may further comprise: resuming charging the DC voltage to the first capacitor after said connecting; and resuming inputting the input signal pattern to the semiconductor device.
Moreover, in the semiconductor device testing method where there are provided a first input switch and a second input switch which connect or disconnect respectively supply of the DC voltage to the first capacitor and the second capacitor, and there are provided a first output switch and a second output switch which connect or disconnect respectively supply of the DC voltage charged in the first capacitor and the second capacitor to the semiconductor device, it is preferably that the disconnecting disconnects supply of the DC voltage charged in the first capacitor to the semiconductor device by switching the first output switch OFF, where the connecting supplies the DC voltage charged in the second capacitor to the semiconductor by switching the second output switch ON and by switching the second input switch OFF, and the resuming resumes charging of the first capacitor with the DC voltage by switching the first input switch ON.
Moreover, the semiconductor device testing method may further comprise: first measuring voltage of the first or second capacitor charged, prior to said testing; second measuring voltage of the first or second capacitor after said testing; first calculating an amount of current consumption of the semiconductor, based on difference between the voltage of the first or second capacitor measured in said first measuring and that measured in said second measuring; and second calculating an average amount of current consumption of the semiconductor, based on result obtained after repeating a plurality of times the first measuring, the second measuring and the first calculating.
Moreover, the semiconductor device testing method may further comprise: measuring voltage of either the first capacitor or the second capacitor; and replacing the first capacitor and the second capacitor anew in the event that voltage of the first capacitor and second capacitor measured in said measuring is less than a predetermined reference voltage.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.